In an Intelligent Resilient Framework (IRF) stack, multiple devices are connected together via stack ports to form a combination device, and a user device manages the combination device, so as to manage all the devices in the IRF stack. In an IRF stack, a single device is called as a member device, and all member devices may be centralized devices or distributed devices, as long as types of the member devices in the same IRF stack are compatible with each other. In the IRF stack, a Master device is one of the member devices, is obtained by role vote and is in charge of managing the whole IRF stack. Only one member device may become the Master device at one time in one stack. A Slave device is one of the member devices, is obtained by role vote, is subject to the Master device, and operates as a backup device of the Master device. In one stack, all devices are Slave devices except the Master device, i.e. there may be multiple Slave devices in the stack. The IRF stack mainly have the following advantages: (1) reducing management; after the IRF stack is formed, a user device may log on the IRF stack by connecting to any port of any member device, which is equivalent to directly logging on the Master device in the IRF stack, and the user device may manage the whole IRF stack and all devices in the IRF stack by configuring the Master device without physically connecting to each member device, distributing IP addresses for the member devices, intercommunicating with the member devices, running router protocols and so on; (2) having a strong network extended capability; the number of ports, bandwidth and processing capability of the IRF stack may be extended easily by adding member devices; (3) having high reliability; the high reliability of the IRF stack may be incarnated by multiple aspects; for example, the IRF stack includes multiple member devices, and the Master device is in charge of operations, managements and maintenances of the IRF stack while the Slave devices may process services when being backups; once the Master device is in failure, the IRF stack will automatically and rapidly vote a new Master device, so as to guarantee that the services of the IRF stack are not interrupted; the physical stack ports between the member devices support an aggregation function, and physical connections between the IRF stack and upper layer devices and between the IRF stack and lower layer devices also support the aggregation function, so that the reliability of the IRF stack is improved by a multi-link backup.
In the IRF stack, the member devices need to be physically connected with each other to make the IRF stack operate normally. A physical port used to a stack connection in a member device is call as a physical stack port, and the physical stack port can not be used in the stack connection unless the physical stack port is bound with a logic stack port (called as a stack port for short). The bound physical stack port can receive and send negotiation messages related to the IRF stack or forward service messages between the member devices.
Specifically, there are two types of connection topology of the physical stack port, including a chain connection and a ring connection. FIG. 1 shows a topology structure of a ring connection. The ring connection is more reliable than the chain connection. When one link in the ring connection is in failure, the function and performance of the IRF stack will not be influenced, while when one link in the chain connection is in failure, the IRF stack will split.
According to the above description, the currently used IRF stack has following disadvantages.
In the IRE stack technologies, when non-broadcast flow is forwarded across a device by using a ring stack, in order to make the overhead in the forwarding process minimal, a critical path method is usually adopted. However, when data are transmitted by using the critical path method, load-sharing can not be performed for the flow. For example, when two devices perform the ring stack, one stack path can only be used as a backup, and thus resources are wasted; when multiple devices perform the ring stack, a stress on flow is brought to direct-connected stack members because of the use of fixed forwarding paths, the flow on the fixed forwarding paths can not be split, and thus a transmitting bottleneck is caused on the fixed forwarding paths. It is taken as an example that the data are transmitted in the ring stack according to the critical path method, as shown in FIG. 2. In FIG. 2, a fixed forwarding path from a Switch 1 to a Switch 5 is from a P1/1 port, to a P4/1 port, to a P4/2 port and to a P5/2 port, and a fixed forwarding path from the Switch 1 to a Switch 4 is from the P1/1 port to the P4/1 port. When there are a large number of data needing to be transmitted from the Switch 1 to the Switch 4, the data are transmitted to the Switch 4 through the path from the P1/1 port to the P4/1 port, and thus a great stress on flow is brought to the path from the P1/1 port to the P4/1 port; at the same time, when there are data needing to be transmitted from the Switch 1 to the Switch 5, the fixed path between the Switch 1 and the Switch 5, i.e. the path from the P1/1 port, to the P4/1 port, to the P4/2 port and to the P5/2, is used to transmit the data. Since there are a large number of data between the P1/1 port to the P4/1 port and a large amount of bandwidth is occupied, the data can not be transmitted to the Switch 5 or the data may be lost during the transmitting process. In other words, when the load on the path from the P1/1 port to the P4/1 port reaches the maximum, the transmitting bottleneck will be caused when newly added flow is transmitted from the Switch 1 to the Switch 4 or from the Switch 1 to the Switch 5, and the data can not be forwarded by using other paths.